Nerve sparing during robot-assisted radical prostatectomy linked to higher risk of ipsilateral positive surgical margins

An analysis of a real-world cohort of patients with prostate cancer who received robot-assisted radical prostatectomy (RARP) found an association between nerve sparing and an increased risk of ipsilateral positive surgical margins.

According to the research, which was published in the Journal of Urology, multivariable analysis demonstrated that nerve sparing was an independent predictor of ipsilateral positive margins (Odds ratio [OR], 1.42; 95% CI, 1.14-1.82).

“The increased risk of positive margins should be considered when counseling patients who opt for nerve sparing robot-assisted radical prostatectomy,” the study authors wrote in their conclusion.

The analysis assessed data from 2574 patients with prostate cancer who received RARP at Dutch teaching hospitals between 2013 and 2018. The hospitals included Martini Hospital Groningen, Hospital Group Twente, St. Antonius Hospital Nieuwegein/Utrecht, and the Canisius Wilhelmina Hospital Nijmegen.

The median patient age was 65, the median preoperative PSA level was 10.6 ng/ml, and the median PSA density was 0.26 ng/ml². Patients’ clinical T stage was T1a/b/c (60%), T2/T2a (27%), T2b (5%), T2c (3%), T3 (5%), or unknown (1%). The Gleason sum scores for patients were ≤6 (19%), 7 (67%), 8 (7%), 9 (7%), or 10 (6 patients). Overall, 86% of patients had preoperative MRI.

The analysis was prospective. Exclusion criteria were prior treatment with salvage RARP or upfront androgen-deprivation therapy. Overall, 5148 prostate lobes were derived from these patients. The investigators assessed each prostate lobe as an individual case, and used a multilevel regression model to evaluate the relationship between nerve sparing and positive surgical margins.

The investigators reported that there were positive surgical margins in 844 (33%) of the 2574 cases. When assessed by pathological stage, the positive margin rate was 23% (n = 353) among the 1533 patients with pT2 disease, and 47% (n = 491) among the 1041 pages with pT3 disease. Sixty-eight percent (n = 1755) of patients received unilateral or bilateral interfascial nerve sparing surgery.

Beyond nerve sparing, the researchers observed several other factors that were significant predicators of positive margins, including prostate specific antigen density (OR 3.64, 95% CI 2.36-5.90). The others were side-specific covariates, including presence of extraprostatic extension on MRI (OR, 1.42; 95% CI 1.03-1.91), percentage of positive cores on systematic biopsy (OR, 3.82; 95% CI 2.50-5.86), and highest preoperative ISUP (International Society of Urological Pathology) biopsy grade (OR, 1.58, 1.62, 2.11 and 4.43, for ISUP grades 2, 3, 4 and 5, respectively).

The researchers noted that their results are inconsistent with multiple prior studies focusing on this topic. They provided 2 potential explanations for the discrepancy.

Regarding the first, the other wrote, “The potential confounders controlled for during analysis in previous studies were prostate specific and not prostate side specific. To determine causality between a nerve sparing approach and ipsilateral positive margins, each prostate lobe should be considered as a separate case.”

The second possible explanation the authors provided related to the design of the multivariable analysis in previous studies, specifically concerning the number and type of covariates that were adjusted for.

“In this study, the large sample size and side specific analysis enabled inclusion of a large number of potential confounders in the multivariable analysis, including the influence of the individual surgeon (and, thus, experience) on the occurrence of positive margins. To our knowledge, none of the previous studies performed an analysis including all of the most important potential predictors, including MRI stage, for positive margins,” the authors wrote.

Reference

Soeterik TFW, van Melick HHE, Dijksman LM, et al. Nerve sparing during robot-assisted radical prostatectomy increases the risk of ipsilateral positive surgical margins. J Urol. 2020;204:91-95.https://doi.org/10.1097/JU.0000000000000760